Isolation and purification of methyl mercaptan oxidase from Rhodococcus rhodochrous for mercaptan detection

Abstract

Methyl mercaptan oxidase was successfully induced from Rhodococcus rhodochrous IGTS8 using methyl mercaptan gas and purified to homogeneity for the detection of mercaptans. The purification procedure involved DEAE-Sephacel and Superose 12 column chromatography with recovery yields of 85.8 and 83.3%, and a specific activity of 92.7 and 303.4 units/mg-protein, respectively. The molecular weight of purified methyl mercaptan oxidase was determined to be 64.5 kDa by SDS-PAGE. The extract from gel filtration chromatography oxidizes methyl mercaptan to produce formaldehyde, which can be easily detected by the purpald-coloring method. Optimum temperature for activity was achieved at 60°C. This enzyme was inhibited by both K2SO4 and NaCl at concentration of less than 100 mM and recovered to original activity at concentration of 200 mM. In the presence of methanol, the activity decreased by 33%.